Rotary drilling pile inclined rock surface step drilling and trimming construction method

Abstract

This invention relates to the technical field of drilling on inclined rock surfaces, and discloses a method for staged drilling and finishing of inclined rock surfaces for rotary cast-in-place piles. The method involves a lower part of the cast-in-place pile hole containing an inclined rock stratum, and a top part containing an inclined rock surface. Based on the high and low points of the inclined rock surface, a side line is formed on the inner wall of the cast-in-place pile hole. A small-diameter drill bit is used to drill downwards along the side line to form a small-diameter step surface. Then, multiple transition drill bits are used sequentially to drill downwards along the side line to form a bottom step surface. The diameters of the transition drill bits gradually increase. Finally, a constant-diameter drill bit, with a diameter matching that of the cast-in-place pile hole, continues drilling downwards along the side line until the inclined rock stratum is cut away, forming a smooth rock surface. By using small-diameter drill bits (from smallest to largest), multiple transition drill bits, and constant-diameter drill bits to perform circumferential cutting and finishing of the inclined rock surface, the finishing range is wide, the rock surface smoothness is good, and this is beneficial for improving the quality of subsequent hard rock drilling.

Description

Technical Field

[0001] This invention patent relates to the technical field of drilling on inclined rock surfaces, and more specifically, to a method for graded drilling and trimming of inclined rock surfaces using rotary cast-in-place piles. Background Technology

[0002] Rotary drilling piles are a common pile foundation technology, widely used in civil engineering fields such as buildings, roads, and bridges.

[0003] In existing technologies, staged reaming drilling or array core drilling is generally used in the construction of rotary cast-in-place piles in hard rock. However, when encountering inclined rock surfaces, regardless of whether staged reaming drilling or array core drilling is used, the rotary drill bit is easily affected by the inclined rock surface, which can easily cause the borehole to deviate, resulting in excessive deviation in the verticality of the borehole, affecting the drilling efficiency and the quality of the borehole. Summary of the Invention

[0004] The purpose of this invention is to provide a method for staged drilling and repair of inclined rock surfaces for rotary cast-in-place piles, which aims to solve the problem in the prior art that when encountering inclined rock surfaces during the drilling of rotary cast-in-place piles in hard rock, the borehole is easily deviated due to the influence of the inclined rock surfaces.

[0005] This invention is implemented as follows: a method for staged drilling and trimming of inclined rock surfaces for rotary cast-in-place piles, comprising the following construction steps:

[0006] 1) The lower part of the cast-in-place pile hole has an inclined rock layer, the top of which has an inclined rock surface exposed in the cast-in-place pile hole. The highest point of the outer periphery of the inclined rock surface coincides with the inner wall of the cast-in-place pile hole to form a high part, and the lowest point of the inclined rock surface corresponds to the low part on the inner wall of the cast-in-place pile hole. The bottom is located directly below the high part. The high part and the low part correspond to form a side line on the inner wall of the cast-in-place pile hole. The extension direction of the side line is consistent with the extension direction of the cast-in-place pile hole.

[0007] Drilling is carried out on an inclined rock surface using a small-diameter cylindrical drill. The outer periphery of the small-diameter cylindrical drill is arranged to coincide with the side line. The diameter of the small-diameter cylindrical drill is smaller than the diameter of the grouting pile hole. The small-diameter cylindrical drill drills on the inclined rock surface to form a small-diameter stepped surface.

[0008] 2) Using multiple transition cylinder drills in sequence, continue drilling downwards at the small-diameter step surface. The outer periphery of the transition cylinder drills coincides with the side line. The diameter of the multiple transition cylinder drills gradually increases. The diameter of the transition cylinder drills is smaller than the diameter of the grouting pile hole and larger than the diameter of the small-diameter cylinder drill.

[0009] The inclined rock surface is drilled sequentially through multiple transition tube drills to form a bottom step surface, which is higher than the lower part.

[0010] 3) Continue drilling downwards on the inclined rock surface using an equal-diameter cylindrical drill, the diameter of which is the same as the diameter of the grouting pile hole, until the equal-diameter cylindrical drill reaches the lower part of the inclined rock surface, cutting away the inclined rock layer, and forming a flat rock surface at the bottom of the grouting pile hole.

[0011] Optionally, the plurality of transition drills include medium-diameter drills and large-diameter drills, wherein the diameter of the medium-diameter drill is greater than the diameter of the small-diameter drill and less than the diameter of the large-diameter drill, and the diameter of the large-diameter drill is less than the diameter of the grouting pile hole.

[0012] In construction step 2), the medium-diameter drill bit is first used to continue drilling downwards at the small-diameter step surface. The outer periphery of the medium-diameter drill bit is arranged to coincide with the side line. The medium-diameter drill bit drills on the inclined rock surface, and the small-diameter step surface is enlarged to form the medium-diameter step surface.

[0013] Then, the large-diameter drill bit is used to continue drilling downwards at the intermediate diameter step surface. The outer periphery of the large-diameter drill bit is arranged to coincide with the side line. The large-diameter drill bit drills on the inclined rock surface, and the intermediate diameter step surface is enlarged to form the bottom step surface.

[0014] Optionally, in construction step 2), if the height distance between the bottom step surface and the lower part is less than the set height, the drilling of the large-diameter tube drill shall be stopped.

[0015] Optionally, in construction step 1), after the small-diameter drill bit has drilled to a set depth, the drilling is stopped, and the small-diameter drill bit idles horizontally on the small-diameter step surface for a set time until the small-diameter step surface is cut and leveled.

[0016] Optionally, in construction step 2), after the intermediate diameter drill bit has drilled to a set depth, the drilling is stopped and the intermediate diameter drill bit idles horizontally on the intermediate diameter step surface for a set time until the intermediate diameter step surface is cut and leveled.

[0017] Optionally, in construction step 2), after the large-diameter drill bit has drilled to a set depth, the drilling is stopped, and the large-diameter drill bit idles horizontally on the bottom step surface for a set time until the bottom step surface is cut and leveled.

[0018] Optionally, in construction step 3), after the equal-diameter barrel drill reaches the lower part of the inclined rock surface, the drilling of the equal-diameter barrel drill is stopped, and the equal-diameter barrel drill idles horizontally on the flat rock surface for a set time until the flat rock surface is cut and leveled.

[0019] Optionally, in the construction arrangement 1), the diameter of the small-diameter barrel drill is greater than 1 / 3 of the diameter of the cast-in-place pile hole and less than 1 / 2 of the diameter of the cast-in-place pile hole.

[0020] Optionally, the small-diameter cylindrical drill has a small-diameter cylindrical cavity with a bottom opening, and the bottom of the small-diameter cylindrical drill is provided with a plurality of cutting teeth, which are arranged at intervals around the outer periphery of the bottom opening of the small-diameter cylindrical cavity.

[0021] The inner wall of the small-diameter cylindrical cavity is provided with a plurality of longitudinal grooves, which are arranged at intervals along the circumference of the small-diameter cylindrical cavity; the bottom of the longitudinal grooves extends to the bottom opening, and the top of the longitudinal grooves extends upward along the axial direction of the small-diameter cylindrical cavity.

[0022] The longitudinal groove is provided with a swing arm that swings up and down. The swing arm has a bottom end face that faces downward and has a plurality of drill teeth. The lower end of the swing arm is hinged to the bottom of the longitudinal groove.

[0023] When the swing arm swings downward to its limit position, the multiple swing arms are arranged flush with the bottom opening, and the drill teeth are arranged flush with the cutting teeth; when the swing arm swings upward to its limit position, the swing arm is stored in the longitudinal groove, and the drill teeth are exposed outside the longitudinal groove.

[0024] In the construction step 1), when the small-diameter drill bit is drilling against the inclined rock surface, the multiple swing arms swing downward to their limit position; as the small-diameter drill bit drills into the inclined rock layer, the multiple swing arms swing upward, and the drill teeth simultaneously cut the inclined rock layer that enters the small-diameter drill bit cavity.

[0025] Optionally, a telescopic rod is connected to the middle of the swing arm, the inner end of the telescopic rod is movably placed in the longitudinal groove, and the outer end of the telescopic rod is hinged to the middle of the swing arm.

[0026] In construction step 1), during the drilling process of the small-diameter barrel drill in the inclined rock strata, the telescopic rod controls the multiple swing arms to swing upwards, and applies a driving force to swing the swing arms downwards in the opposite direction, thereby increasing the force of the drill teeth cutting the inclined rock strata that enter the small-diameter barrel cavity.

[0027] Compared with existing technologies ， The present invention provides a method for staged drilling and trimming of inclined rock surfaces for rotary cast-in-place piles. Based on the highest and lowest points of the inclined rock surface, a side line is formed on the inner wall of the cast-in-place pile hole on one side of the highest point. First, a small-diameter barrel drill is used to drill downward along the side line to form a small-diameter step surface. The small-diameter drill has low torque and can quickly cut and trim the inclined rock surface. Then, multiple transition barrel drills are used in sequence to continue drilling downward along the small-diameter step surface. The diameter of the multiple transition barrel drills gradually increases, and each drilling goes down to a certain depth, eventually forming a bottom step surface. Then, an equal-diameter barrel drill is used to continue drilling downward on the inclined rock surface. The diameter of the equal-diameter barrel drill is the same as the diameter of the cast-in-place pile hole, until the inclined rock layer is cut away to form a flat rock surface.

[0028] In this way, the inclined rock surface is circumferentially cut, broken, and repaired using small-diameter drill barrels with increasing diameters, multiple transition drill barrels, and equal-diameter drill barrels. Utilizing the principle that small-diameter drill barrels have low torque and can quickly cut and repair inclined rock surfaces, the process involves staged drilling and gradual diameter expansion to achieve rapid repair of inclined rock strata. Simultaneously, by following the side line during drilling and constantly observing whether the drill rod is vertical, the process ensures that the highest and lowest elevation differences in the drilling area for each pass are within a set range. This effectively avoids borehole tilting, achieves a wide repair range, and results in good rock surface flatness, which is beneficial for improving the quality of subsequent hard rock drilling. Attached Figure Description

[0029] Figure 1 This is a front view schematic diagram of the inclined rock strata provided by the present invention;

[0030] Figure 2 This is a construction diagram of small-diameter barrel drilling provided by the present invention;

[0031] Figure 3 This is a construction diagram of medium-diameter barrel drilling provided by the present invention;

[0032] Figure 4 This is a construction diagram of large-diameter barrel drilling provided by the present invention;

[0033] Figure 5 This is a construction diagram of equal-diameter barrel drilling provided by the present invention;

[0034] Figure 6 This is a cross-sectional schematic diagram of the small-diameter cylindrical drill provided by the present invention;

[0035] Figure 7 This is a cross-sectional schematic diagram of the small-diameter cylindrical drill provided by the present invention;

[0036] Figure 8 This is a front view schematic diagram of the small-diameter stepped surface provided by the present invention;

[0037] Figure 9 This is a front view schematic diagram of the middle diameter stepped surface provided by the present invention;

[0038] Figure 10 This is a front view schematic diagram of the bottom stepped surface provided by the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0040] The implementation of the present invention will be described in detail below with reference to specific embodiments.

[0041] In the accompanying drawings of this embodiment, the same or similar reference numerals correspond to the same or similar components. In the description of this invention, it should be understood that if terms such as "upper," "lower," "left," and "right" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, they are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the accompanying drawings are only for illustrative purposes and should not be construed as limiting this patent. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0042] Reference Figure 1-10 The image shown is a preferred embodiment of the present invention.

[0043] The present invention provides a method for staged drilling and finishing of inclined rock surfaces (101 steps) for rotary cast-in-place piles, comprising the following construction steps:

[0044] 1) The lower part of the cast-in-place pile hole has an inclined rock layer 100, and the top of the inclined rock layer 100 has an inclined rock surface 101 exposed in the cast-in-place pile hole. The highest point of the outer periphery of the inclined rock surface 101 coincides with the inner wall of the cast-in-place pile hole to form a high part 10, and the lowest point of the inclined rock surface 101 corresponds to the low part 20 on the inner wall of the cast-in-place pile hole. The bottom part 20 is located directly below the high part 10. The high part 10 and the low part 20 correspond to the side line 30 on the inner wall of the cast-in-place pile hole. The extension direction of the side line 30 is consistent with the extension direction of the cast-in-place pile hole.

[0045] A small-diameter drill 200 is used to drill on the inclined rock surface 101. The outer periphery of the small-diameter drill 200 coincides with the side line 30. The diameter of the small-diameter drill 200 is smaller than the diameter of the grouting pile hole. The small-diameter drill 200 drills on the inclined rock surface 101 to form a small-diameter stepped surface 102.

[0046] 2) Using multiple transition tube drills in sequence, continue drilling downwards at the small-diameter step surface 102. The outer periphery of the transition tube drills coincides with the side line 30. The diameter of the multiple transition tube drills gradually increases. The diameter of the transition tube drills is smaller than the diameter of the grouting pile hole, but larger than the diameter of the small-diameter tube drill 200.

[0047] After the inclined rock surface 101 is drilled through multiple transition tube drills in sequence, a bottom step surface 104 is formed, which is higher than the lower part 20.

[0048] 3) Using the equal diameter barrel drill 500, continue drilling downwards on the inclined rock surface 101. The diameter of the equal diameter barrel drill 500 is the same as the diameter of the grouting pile hole, until the equal diameter barrel drill 500 drills into the lower part 20 of the inclined rock surface 101, cutting away the inclined rock layer 100, and forming a flat rock surface at the bottom of the grouting pile hole.

[0049] The above-mentioned rotary drilling and grouting method for inclined rock surface 101 is as follows: Based on the highest and lowest points of the inclined rock surface 101, a side line 30 is formed on the inner wall of the grouting pile hole on one side of the highest point. First, a small-diameter barrel drill 200 is used to drill downward along the side line 30 to form a small-diameter step surface 102. The small-diameter drill has low torque, which can quickly cut and grout the inclined rock surface 101. Then, multiple transition barrel drills are used in sequence to continue drilling downward along the small-diameter step surface 102. The diameter of the multiple transition barrel drills gradually increases, and each drilling goes down to a certain depth, eventually forming a bottom step surface 104. Then, an equal-diameter barrel drill 500 is used to continue drilling downward on the inclined rock surface 101. The diameter of the equal-diameter barrel drill 500 is the same as the diameter of the grouting pile hole, until the inclined rock layer 100 is cut away to form a flat rock surface.

[0050] In this way, the inclined rock surface 101 is circumferentially cut, broken, and repaired by using small-diameter drill barrels 200 (from small to large diameter), multiple transition drill barrels, and equal-diameter drill barrels 500. Utilizing the principle that small-diameter drill barrels have low torque and can quickly cut and repair the inclined rock surface 101, staged drilling is performed to gradually expand the diameter, achieving rapid repair of the inclined rock layer 100. At the same time, by drilling downwards while adhering to the side line 30 during the drilling process and constantly observing whether the drill rod is vertical, borehole tilting is effectively avoided, resulting in a wide repair range, good rock surface flatness, and improved quality of subsequent hard rock drilling.

[0051] By utilizing the principle that a small-diameter drill barrel with low torque can quickly cut and trim inclined rock surfaces 101, the drilling is carried out in stages, gradually expanding the diameter to improve the speed of trimming inclined rock layers 100. At the same time, by drilling downwards while keeping in contact with the side line 30 during the drilling process and constantly observing whether the drill rod is vertical, the borehole tilting is effectively avoided.

[0052] In this embodiment, the multiple transition drills include a medium-diameter drill 300 and a large-diameter drill 400. The diameter of the medium-diameter drill 300 is larger than the diameter of the small-diameter drill 200 and smaller than the diameter of the large-diameter drill 400. The diameter of the large-diameter drill 400 is smaller than the diameter of the grouting pile hole.

[0053] In construction step 2), the medium diameter drill 300 is used to continue drilling downward at the small diameter step surface 102. The outer periphery of the medium diameter drill 300 coincides with the side line 30. The medium diameter drill 300 drills on the inclined rock surface 101. The small diameter step surface 102 is enlarged to form the medium diameter step surface 103.

[0054] Then, using a large-diameter drill bit 400, drilling continues downwards at the intermediate-diameter step surface 103. The outer periphery of the large-diameter drill bit 400 coincides with the side line 30. Drilling is carried out on the inclined rock surface 101 of the large-diameter drill bit 400, and the hole is enlarged at the intermediate-diameter step surface 103 to form the bottom step surface 104. In this way, the diameter is gradually enlarged, and drilling proceeds downwards step by step along the side line 30.

[0055] In construction step 2), once the height distance between the bottom step surface 104 and the lower part 20 is less than the set height, the drilling of the large-diameter barrel drill 400 is stopped. This avoids excessive height difference and excessive residue in the retained inclined rock strata 100, which would cause the equal-diameter barrel drill 500 to tilt and have low efficiency when drilling down.

[0056] In a preferred embodiment, in construction step 1), after the small-diameter drill 200 has drilled to the set depth, the drilling of the small-diameter drill 200 is stopped, and the small-diameter drill 200 idles horizontally on the small-diameter step surface 102 for a set time until the small-diameter step surface 102 is cut and leveled. In this way, the hard rock is fully cut and trimmed through in-situ circumferential cutting.

[0057] In a preferred embodiment, in construction step 2), after the medium diameter drill 300 drills to the set depth, drilling is stopped, and the medium diameter drill 300 idles horizontally on the medium diameter step surface 103 for a set time until the medium diameter step surface 103 is cut and leveled. In this way, the hard rock is fully cut and trimmed through in-situ circumferential cutting.

[0058] In a preferred embodiment, in construction step 2), after the large-diameter drill 400 has drilled to the set depth, drilling is stopped, and the large-diameter drill 400 idles horizontally on the bottom step surface 104 for a set time until the bottom step surface 104 is cut and leveled. In this way, the hard rock is fully cut and trimmed through in-situ circumferential cutting.

[0059] In a preferred embodiment, in construction step 3), after the equal-diameter drill 500 drills to the lower part 20 of the inclined rock surface 101, the drilling of the equal-diameter drill 500 is stopped, and the equal-diameter drill 500 idles horizontally on the flat rock surface for a set time until the flat rock surface is cut and leveled. In this way, the hard rock is fully cut and trimmed through in-situ circumferential cutting.

[0060] In construction layout 1), the diameter of the small-diameter drill bit 200 is greater than 1 / 3 of the diameter of the cast-in-place pile hole, but less than 1 / 2 of the diameter of the cast-in-place pile hole. This ensures that the small-diameter drill bit 200 has a large torque, thus ensuring construction efficiency.

[0061] In a preferred embodiment, the drilling depth each time does not exceed one-third of the length of the side line 30.

[0062] In this embodiment, the small-diameter cylindrical drill 200 has a small-diameter cylindrical cavity with a bottom opening, and the bottom of the small-diameter cylindrical drill 200 is provided with a plurality of cutting teeth, which are arranged at intervals around the outer periphery of the bottom opening of the small-diameter cylindrical cavity.

[0063] The inner wall of the small-diameter cylindrical cavity is provided with a plurality of longitudinal grooves 201, which are arranged at intervals along the circumference of the small-diameter cylindrical cavity; the bottom of the longitudinal grooves 201 extends to the bottom opening, and the top of the longitudinal grooves 201 extends upward along the axial direction of the small-diameter cylindrical cavity.

[0064] The longitudinal groove 201 is provided with a swing arm 600 that swings up and down. The swing arm 600 has a bottom end face that faces downward and is provided with a plurality of drill teeth 601. The lower end of the swing arm 600 is hinged to the bottom of the longitudinal groove 201.

[0065] When the swing arm 600 swings downward to its limit position, the multiple swing arms 600 are arranged flush with the bottom opening, and the drill teeth 601 are arranged flush with the cutting teeth; when the swing arm 600 swings upward to its limit position, the swing arm 600 is stored in the longitudinal groove 201, and the drill teeth 601 are exposed outside the longitudinal groove 201.

[0066] In construction step 1), when the small-diameter drill 200 is drilling into the inclined rock surface 101, multiple swing arms 600 swing downwards to their limit positions. As the small-diameter drill 200 drills into the inclined rock layer 100, multiple swing arms 600 swing upwards, and the drill teeth 601 simultaneously cut into the inclined rock layer 100 that has entered the small-diameter drill cavity. Thus, after the small-diameter drill 200 is embedded into the inclined rock layer 100 to a certain depth, the swing arms 600 swing upwards under the contact of the inclined rock layer 100, while the drill teeth 601 cut into the inclined rock layer 100, causing it to break and generate a large amount of rock debris. This rock debris can fill the space between the drill wall and the outer periphery of the inclined rock layer 100 embedded in the small-diameter drill cavity, greatly increasing the friction and facilitating core extraction. At the same time, the embedding of the drill teeth 601 into the rock layer also facilitates core extraction through in-situ circumferential cutting.

[0067] In this embodiment, a telescopic rod 610 is connected to the middle of the swing arm 600. The inner end of the telescopic rod 610 is movably placed in the longitudinal groove 201, and the outer end of the telescopic rod 610 is hinged to the middle of the swing arm 600.

[0068] In construction step 1), during the drilling process of the small-diameter drill 200 into the inclined rock stratum 100, the telescopic rod 610 controls multiple swing arms 600 to swing upwards, and applies a driving force in the opposite direction to swing the swing arms 600 downwards, increasing the force with which the drill teeth 601 simultaneously cut the inclined rock stratum 100 entering the small-diameter drill cavity. This causes the drill teeth 601 to cut the inclined rock stratum 100, breaking it and generating a large amount of rock debris. This rock debris can fill the space between the drill wall and the outer periphery of the inclined rock stratum 100 embedded in the small-diameter drill cavity, greatly increasing friction and facilitating core extraction. Simultaneously, the embedding of the drill teeth 601 into the rock stratum also facilitates core extraction through in-situ circumferential cutting.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for staged drilling and trimming of inclined rock surfaces for rotary cast-in-place piles, characterized in that, The construction steps include the following: 1) The lower part of the cast-in-place pile hole has an inclined rock layer, and the top of the inclined rock layer has an inclined rock surface exposed in the cast-in-place pile hole. The highest point of the outer periphery of the inclined rock surface coincides with the inner wall of the cast-in-place pile hole to form a high part, and the lowest point of the inclined rock surface corresponds to the low part on the inner wall of the cast-in-place pile hole. The low part is located directly below the high part, and the high part and the low part correspond to form a side line on the inner wall of the cast-in-place pile hole. The extension direction of the side line is consistent with the extension direction of the cast-in-place pile hole. A small-diameter drill bit is used to drill on an inclined rock surface, with the outer periphery of the drill bit coinciding with the side line. The diameter of the small-diameter drill bit is smaller than the diameter of the grouting pile hole. The small-diameter drill bit drills on the inclined rock surface to form a small-diameter stepped surface. 2) Using multiple transition cylinder drills in sequence, continue drilling downwards at the small-diameter step surface. The outer periphery of the transition cylinder drills coincides with the side line. The diameter of the multiple transition cylinder drills gradually increases. The diameter of the transition cylinder drills is smaller than the diameter of the grouting pile hole and larger than the diameter of the small-diameter cylinder drill. The inclined rock surface is drilled sequentially through multiple transition tube drills to form a bottom step surface, which is higher than the lower part. 3) Continue drilling downwards on the inclined rock surface using an equal-diameter cylindrical drill, the diameter of which is the same as the diameter of the grouting pile hole, until the equal-diameter cylindrical drill reaches the lower part of the inclined rock surface, cutting away the inclined rock layer, and forming a flat rock surface at the bottom of the grouting pile hole. The plurality of transition drills include medium-diameter drills and large-diameter drills, wherein the diameter of the medium-diameter drill is greater than the diameter of the small-diameter drill and less than the diameter of the large-diameter drill, and the diameter of the large-diameter drill is less than the diameter of the grouting pile hole. In construction step 2), the medium-diameter drill bit is first used to continue drilling downwards at the small-diameter step surface. The outer periphery of the medium-diameter drill bit is arranged to coincide with the side line. The medium-diameter drill bit drills on the inclined rock surface, and the small-diameter step surface is enlarged to form the medium-diameter step surface. Then, the large-diameter drill bit is used to continue drilling downwards at the intermediate diameter step surface. The outer periphery of the large-diameter drill bit is arranged to coincide with the side line. The large-diameter drill bit drills on the inclined rock surface, and the intermediate diameter step surface is enlarged to form the bottom step surface.

2. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 1, characterized in that, In construction step 2), once the height distance between the bottom step surface and the lower part is less than the set height, the large-diameter cylinder drilling is stopped.

3. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 1, characterized in that, In construction step 1), after the small-diameter drill bit has drilled to a set depth, the drilling is stopped. The small-diameter drill bit then idles horizontally on the small-diameter step surface for a set time until the small-diameter step surface is cut and leveled.

4. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 1, characterized in that, In construction step 2), after the intermediate diameter drill bit has drilled to the set depth, the drilling is stopped. The intermediate diameter drill bit then idles horizontally on the intermediate diameter step surface for a set time until the intermediate diameter step surface is cut and leveled.

5. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 1, characterized in that, In construction step 2), after the large-diameter drill bit has drilled to the set depth, the drilling is stopped and the large-diameter drill bit is left to idle horizontally on the bottom step surface for a set time until the bottom step surface is cut and leveled.

6. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 1, characterized in that, In construction step 3), after the equal-diameter barrel drill reaches the lower part of the inclined rock surface, the drilling of the equal-diameter barrel drill is stopped, and the equal-diameter barrel drill idles horizontally on the flat rock surface for a set time until the flat rock surface is cut and leveled.

7. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 1, characterized in that, In the construction arrangement 1), the diameter of the small-diameter cylindrical drill is greater than 1 / 3 of the diameter of the cast-in-place pile hole and less than 1 / 2 of the diameter of the cast-in-place pile hole.

8. The method for graded drilling and trimming of inclined rock surface for rotary cast-in-place piles as described in any one of claims 1 to 7, characterized in that, The small-diameter cylindrical drill has a small-diameter cylindrical cavity with a bottom opening, and the bottom of the small-diameter cylindrical drill is provided with multiple cutting teeth, which are arranged at intervals around the outer periphery of the bottom opening of the small-diameter cylindrical cavity. The inner wall of the small-diameter cylindrical cavity is provided with a plurality of longitudinal grooves, which are arranged at intervals along the circumference of the small-diameter cylindrical cavity; the bottom of the longitudinal grooves extends to the bottom opening, and the top of the longitudinal grooves extends upward along the axial direction of the small-diameter cylindrical cavity. The longitudinal groove is provided with a swing arm that swings up and down. The swing arm has a bottom end face that faces downward and has a plurality of drill teeth. The lower end of the swing arm is hinged to the bottom of the longitudinal groove. When the swing arm swings downward to its limit position, the multiple swing arms are arranged flush with the bottom opening, and the drill teeth are arranged flush with the cutting teeth; when the swing arm swings upward to its limit position, the swing arm is stored in the longitudinal groove, and the drill teeth are exposed outside the longitudinal groove. In construction step 1), when the small-diameter drill bit is drilling against the inclined rock surface, the multiple swing arms swing downward to their limit position; as the small-diameter drill bit drills into the inclined rock layer, the multiple swing arms swing upward, and the drill teeth simultaneously cut the inclined rock layer that enters the small-diameter drill bit cavity.

9. The method for graded drilling and trimming of inclined rock surfaces for rotary cast-in-place piles as described in claim 8, characterized in that, A telescopic rod is connected to the middle of the swing arm. The inner end of the telescopic rod is movably placed in the longitudinal groove, and the outer end of the telescopic rod is hinged to the middle of the swing arm. In construction step 1), during the drilling process of the small-diameter barrel drill in the inclined rock strata, the telescopic rod controls multiple swing arms to swing upwards and applies a driving force to swing the swing arms downwards in the opposite direction, thereby increasing the force of the drill teeth synchronously cutting the inclined rock strata entering the small-diameter barrel cavity.

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